1. Field of the Invention
The present invention relates generally to a compressor that is driven by an electric motor wherein the lubricant of the compressor is used to cool the electric motor and, more specifically, to a screw compressor with a variable reluctance motor mounted above the compressor with the lubricant of the compressor being used to cool the variable reluctance motor prior to flowing into the compressor.
2. Description of the Prior Art
Many different types of motor driven compressors are known to those skilled in the art. In addition, it is also known to mount the motor vertically above the compressor.
U.S. Pat. No. 4,545,742, which issued to Schaefer on Oct. 8, 1985, describes a vertical axis helical screw compressor that is provided with a discharge gas oil mist eliminator and dual transfer tube manifold that is used for supplying liquid refrigerant and refrigerant vapor to the compression area. Refrigerant vapor discharges from the compressor through the rotor of the electric motor. This discharge is then directed toward a deflector for the purpose of causing oil mist in the discharge to adhere to the deflector and be separated from the gaseous discharge. The separated oil then drops from the deflector into the bottom of an enclosure which functions as an oil sump.
U.S. Pat. No. 1,080,737, which issued to VerPlanck on Dec. 9, 1913, discloses an internal combustion engine which utilizes water to cool the engine. It is intended for use with high compression engines. It supplies low pressure air for scavenging purpose and high pressure air for use in injecting fuel into the cylinder of the engine.
U.S. Pat. 3,514,225, which issued to Monden et al on May 26, 1970, illustrates and describes a motor driven compressor for use in a refrigeration application. It comprises a hermetically sealed casing which contains the motor compressor and a lubricant fluid. A suction cup is connected in series with a suction pipe and is maintained in heat exchange relationship with the lubricant.
U.S. Pat. No. 3,572,978, which issued to Scheidorf on Mar. 30, 1971, discloses a hermetically sealed compressor having a means for cooling a lubricant fluid. The motor is mounted above the compressor and is connected to the compressor by a vertical drive shaft. A longitudinally extending lubricant passage in the shaft is connected to a passage at the upper end of the shaft. A pump is used to provide a flow of lubricant through the longitudinal and transverse passages of the apparatus. A discharge of lubricant passes over the top of the motor and into the casing during a period of maximum flow of lubricant and on to the motor when the lubricant flow is less than its maximum. It does not utilize a screw compressor. Furthermore, it does not describe a variable reluctance motor or an apparatus in which the oil is used by the compressor.
U.S. Pat. No. 3,663,127, which issued to Cheers on May 16, 1972, describes a hermetically sealed compressor oil cooling system. The device is provided with a vertical shaft and an electric motor that is mounted above the gas pump. The end turns of the motor are disposed in a direct path of the lubricating oil which is flung from the outlet of a crankshaft oil passage that is, in turn, fed from an oil pump in the sump of the compressor. The oil is caused to flow against the main winding of the motor to cool the motor.
U.S. Pat. No. 3,922,114, which issued to Hamilton et al on Nov. 25, 1975, discloses a hermetically sealed rotor screw compressor with an improved oil management system. A two part housing is provided with a first sealed chamber and an upper chamber carrying the electric motor. It also comprises a lower chamber mounted in vertical association with the upper chamber. The discharge gas, which includes entrained oil, passes through ducts within the motor to cool the motor. The entrained oil is discharged against the upper end of a cylindrical housing to separate some of the oil from the discharge gas as a result of centrifugal force. The discharge gas is directed downwardly to further cool the motor. The oil then drains to the bottom of the enclosure which forms an oil sump.
U.S. Pat. No. 4,780,061, which issued Butterworth on Oct. 25, 1988, discloses a screw compressor that is provided with an integral oil cooling system. It includes a motor housing section and a compressor section with an oil separator downstream of the compressor discharge port. Suction gas is directed to a working chamber of the compressor so that the compressor drive motor is cooled by suction gas. Oil is directed into the passage of the motor housing heat exchange structure prior to the delivery of the oil to the compressor surfaces that require lubrication. The oil is cooled by the suction gas which passes over the surface of the heat exchanger structure.
U.S. Pat. No. 4,802,826, which issued to Hall on Feb. 7, 1989, illustrates a sealed and self contained liquid cooled gas compressor. It is completely sealed and is made up of a vertically superimposed motor and gas compressor. Heat exchanger tubes are mounted within the oil sump and in an externally mounted heat exchanger for the purpose of cooling the oil in the sump. The cooled oil is caused to continually flow over the electric motor and compressor to provide cooling and lubrication along with sealing of the compressor pistons. This device does not disclose the use of a screw compressor or the use of a variable reluctance motor. Furthermore, the oil does not flow through the inside portion of the motor and, in addition, the fluid does not leave the containment which surrounds the motor and compressor.
U.S. Pat. 4,477,233, which issued to Schaefer on Oct. 16, 1984, discloses a vertical axis screw compressor with a discharge gas oil mist eliminator and a dual transfer tube manifold for supplying liquid refrigerant and refrigerant vapor to the compression area of the compressor. It does not describe the use of a variable reluctance motor. It illustrates a hermetically sealed unit which causes oil liquid to drop down onto the stator of a motor after the oil liquid is separated from the discharge gas. The cooling of the motor occurs after the oil passes from the discharge port of the compressor.
U.S. reissue Pat. No. 30,994, which was reissued to Shaw on Jul. 13, 1982, describes a vertical axis hermetically sealed rotary helical screw compressor with an improved oil management system for its rotor bearings. It does not describe a variable reluctance motor and the oil flows to the motor after it is separated from the exhaust gas from the compressor.
U.S. Pat. No. 4,181,474, which issued to Shaw on Jan. 1, 1980, discusses a vertical axis hermetically sealed rotary helical screw compressor that is provided with a cylindrical housing that is coaxially mounted with an outer enclosure. Oil is bled from a sump and directed to the suction inlet tube of the compressor. The discharge from the compressor is directed axially downward with the lower tapered roller bearing assembly providing a minimal high pressure gap between the screw rotor ends and the stationary end plates.
U.S. Pat. 4,645,429, which issued to Asami et al on Feb. 24, 1987, describes a rotary compressor in which the discharged gas is cooled by heat dissipation through a heat exchanger after which it is again returned to the compressor. The lubricant oil is also cooled. Every component of the compressor main body and the electric motor is cooled by causing the cooled discharge gas to pass through the motor and suppress the temperature rise of the compressor.
None of the prior art devices described above teach the concept of directing cooled lubricant through the variable reluctance motor to cool its stator components prior to being directed to the inlet duct of the compressor where it acts as a lubricant for the compressor.